PROJECT SUMMARY/ABSTRACT PROJECT 10: DEVELOPMENT OF AUDIOVISUAL SPEECH ENHANCEMENT IN CHILDREN Children are at a disadvantage relative to adults when listening to speech that is degraded by auditory background noise. One highly robust cue that adults use to compensate for noisy environments is visual speech. The increased accuracy and efficiency of speech processing in the presence of visual speech is called audiovisual (AV) speech enhancement. In adults, these enhancements occur via two neutrally distinct mechanisms: a perceptual mechanism and a linguistic mechanism. Although a few studies have been undertaken to quantify AV speech enhancement in children, most researchers have overlooked the plurality of the mechanisms that underlie such enhancements. The long-term goal of my research program is to provide a cohesive theoretical account of the development of AV speech enhancement. The objective of the current proposal is to characterize the development of the perceptual and linguistic mechanisms that underlie AV speech enhancement. Aim 1 examines development of the perceptual mechanism of AV speech enhancement. It will evaluate the extent to which adults and 5- to 14-year-old children use visual temporal cues to predict the timing of onsets and peaks in the amplitude envelope of auditory speech, thereby improving detection and recognition of auditory speech in noise. It is hypothesized that children as young as 5 years old benefit from the perceptual mechanism of AV speech enhancement, such as simultaneous onsets, but that it takes longer to learn to use the ongoing correlations between the auditory and visual amplitude envelopes to precisely track connected auditory speech. Aim 2 examines development of the linguistic mechanism of AV speech enhancement. It evaluates the extent to which 5- to 14-year-old children apply visual phonetic knowledge to constrain phonetic interpretation. This aim will test the hypothesis that, with increasing age, children demonstrate increasingly detailed visual phonetic knowledge and consequent decreases in visually salient AV errors. I expect that ability to use visual speech to supplement phonetic interpretation will reach maturity later in development than the ability to use visual temporal cues to aid perceptual processing. The proposed research will address a critical gap in our understanding of how children use visual speech to compensate for adverse auditory conditions in the real world. Clinically, this work has profound implications for age-appropriate rehabilitation and education practices for children with hearing loss.